void VS( float3 vPosIn     : POSITION,
         float4 vDiffuseIn : COLOR,
         float2 uv_in      : TEXCOORD0,   // .xy = UVs to use, .zw = IGNORE
         float2 rad_ang_in : TEXCOORD1,   // .xy = rad, ang
     out float4 vPosProj : POSITION,
     out float4 vDiffuse : COLOR, 
     out float2 uv       : TEXCOORD,
     out float2 rad_ang  : TEXCOORD1 )
{  
    vPosProj = float4(vPosIn.x, vPosIn.y, vPosIn.z, 1);
    vDiffuse = vDiffuseIn;
    uv = uv_in.xy;
    rad_ang = rad_ang_in;
}